Method of making same



Patented Aug. 28, 1945 METHOD OF MAKING SAME Richard s. Reynolds, Richmond, Va.

Application November 1, 1941, Serial No. 417,578

. 3 Claims.

The present invention has for its object to provide an aluminum-alloy sheet composed of layers of aluminum alloys of difierent characteristics and which are mutually resistant to bonding. As an example, certain aluminum alloys have marked resistance to fatigue and hav relatively high yield strength, and yet do not possess substantial resistance to abrasion in handling. Other aluminum alloys lack the stated or other qualities and, at the same time, are highly resistant to abrasion. In order to combine in one structure the advantage of both alloys, it has been proposed toroll together assembled slabs of the alloys in order to produce a composite sheet, but this was established as impractical because of poor adherence.

I have discovered a method of overcoming the problem which has heretofore prevented the commercial production of such composite aluminu alloy sheets.

In the drawing I have diagrammatically shown a composite aluminum alloy sheet in which i represents a greatly enlarged alloy sheet, as, for example, of aluminum, copper, manganese and magnesium, and 2 indicates the commercially pure aluminum bond, 3 representing an alloy sheet, as, for example, aluminum silicon, magnesium and chromium.

As a specific example, for a basic alloy slab I may employ aluminum alloyed with copper, manganese and magnesium, such as in the approximate percentages of 4.2% copper, 0.6% manganese, and 1.5% magnesium. This alloy has a specific gravity of 2.76 and weight in pounds per cubic inch of 0.100. It is therefore light, and

it has initial relatively high'yield strength. When annealed, it has a hardness of 42 Brinell which is very substantially increased by heat treatment alloy specified above.

and, quenching and by hot rolling. one primary characteristic of the alloy is its resistance to fatigue, which remains substantially constant, the

factor not beingv substantially changed by heat treatment.

Continuing the specific example, for-the associated alloy slab or slabs, I may employ aluminum alloyed with silicon, magnesium and chromium such as in the approximatepercentages 0.7% silicon, 1.25% magnesium and 0.25% chromium.

I Such. alloy material'has a weight in pounds per cubic inch of 0.007 and a specific gravity of 2.69, with a hardness exceeding 40 Brinell in annealed state.

minum contains small percentages oriron, silicon and copper, the latter two materials being in lesser degree and the total of these common alloys being upwards of 1%. Thus commercially pure" aluminum may be employed for my bonding material. 1

Particularly, a' s'calped ingot of the so-called basic alloy, which may be of any desired thickness, such as 5", may have applied to the opposite faces thereof thinner plates or sheets such asplates of 0.250" composed of the associated Intermediate the ingot and each of the associated plates, I interpose a sheet of commercially pure aluminum which may be .020" thick, that thickness being sufllcient to insure exceedingly thin but uniform bonding layers in the final composite sheet.

The composite body, generally heated as in standard ingot rolling practice, is then rolled down to the thickness desired for the specific purpose as, for example, one of the customary sheet thicknesses extensively used in the aircraft industry. By following this method, I have found that the layers are permanently bonded into an integral structure. In the specific example, the aluminum-alloy sheet thus produced embodies in one structur the advantageous qualities oi both the base and the associated alloy structures, the surface exposed alloy associated with the basic alloy-being resistant to abrasion and possessing other inherent characteristics, so that the composite body has marked advantages over a sheet made of the composite alloys, according to usual practice.

It will be understood that the specific example is used to illustrate the invention, and the invention is capable of wide application to the association of aluminum-alloy bodies which resist ins a plurality oihard aluminum-alloy layers exceeding 40 Brinell in hardness, the layers being Between the basic and each associated slab, I

characterized by resistance to mutual bonding under pressure, and intermediate each two layers a' toll of commercially pure aluminum bonding the assembly into a permanent integral sheet structure, the aluminum bonding containing less than 1% silicon.

2. A composite metallic sheet comprising a plurality of hard aluminum-alloy layers exceeding 40 Brinell in hardness, and intermediate each Aug. 28', 1945.

Filed May 2'7, 1944 Z 5 R Y ma m N R w Mm m m: b m m M v w 

